The present invention relates to a ball valve connected to pipe arrangement for the passage of cold or hot water, gas, etc. and, more particularly, to a multipurpose ball valve capable of opening and closing a fluid flow passage, preventing a fluid from a counter flow, discharging a fluid in pipe arrangement on the downstream side, and confirming whether or not a fluid leaks out of or escapes from the pipe arrangement on the downstream side or the ball valve per se.
A ball valve with a built-in check valve and a ball valve with a discharge port for a fluid in pipe arrangement on the downstream side have heretofore been proposed. However, there has not yet been proposed any ball valve with both a check valve and a discharge port.
In mounting a conventional ball valve with a built-in check valve, a discharge port has been formed in pipe arrangement on the downstream side. For this reason, when pipes are arranged vertically and a fluid flows upwardly, it is impossible to discharge a fluid present in a portion of the pipe arrangement between the ball valve and the discharge port.
In mounting a conventional ball valve with a discharge port, a check valve has been required to be mounted on pipe arrangement on the upstream side. This is because a fluid in the pipe arrangement on the downstream side cannot be discharged out if the check valve should be mounted on the pipe arrangement on the downstream side. However, even if the check valve is mounted on the downstream side, when a fluid is liquid, there is a fair possibility of the liquid present in a portion of the pipe arrangement between the ball valve and the check valve undergoing thermal expansion which will extraordinarily increase the internal pressure of the pipe arrangement to cause leakage of the liquid from portions of the pipe arrangement connected to the ball valve and check valve and cause malfunction of the ball valve and check valve. Furthermore, the ball valves of this type are complicated in construction of an inside fluid flow passage and in overall structure and, therefore, the manufacturing cost thereof will become high. In addition, since the discharge port is generally formed in the bottom of a valve casing for the ball valve, when pipes are arranged along the surface of a wall, it will be difficult to connect a pipe to the discharge port and to discharge a fluid through the discharge port.